1. Field of the Invention
The present invention relates to a cable reel in which an electrical connection between a fixed body and a movable body is made through a flat cable. More particularly, it relates to a cable reel suitable for installing on an expandable and contractible steering device of a vehicle, the device having a telescopic function.
2. Description of the Related Art
In cable reels, one end of a plurality of turns of a flat cable is secured to and led out of fixed bodies, whereas the other end of the cable is secured to and led out of movable bodies. When the movable body rotates, it rotates through a predetermined angle by virtue of the fact that the flat cable is caused to wind toward the side of the movable body, or to re-wind from it. Cable reels are installed on steering devices of automobiles in order to serve as air bag circuits, horn circuits or cruise control circuits (Japanese Patent Unexamined Publication No. 57-66043).
When such a cable reel is incorporated into a steering device, the movable body is secured to the side of a steering wheel, while the fixed body is secured to members of the fixed side of a column cover or the like. The flat cable led out of the fixed body is connected to a connector on the fixed side. In a steering device equipped with a so-called telescopic function, in which a steering wheel can be adjusted in the axial direction of the steering shaft, since the distance between the cable reel body and the connector changes during the movement of the steering wheel, a leading section which is led from the fixed body of the flat cable must be designed long enough to allow for the amount of the distance change.
When the leading section of the flat cable becomes long, because it becomes an obstacle if left slack, a storage device, for example, as disclosed in Japanese Patent Examined Publication No. 63-32527 is required. In such a storage device, a harness spool is provided between the movable side and the fixed side of a steering device with the telescopic function. At the same time, a plurality of wire harnesses led out of the steering wheel are housed in the harness spool while being helically wound. The movement of the steering wheel in the axial direction is thus absorbed by changing the radii of the wire harnesses wound in the harness spool.
According to the above-mentioned conventional storage device, during the telescopic operation, e.g., when the steering wheel is pulled toward the driver, the radii of the wound wire harnesses change in the direction in which they become small. On the other hand, when the steering wheel is pushed, the radii of the wound wire harnesses change in the direction in which they become large. Since the radii of the wound wire harnesses can be changed within the harness spool, long wire harnesses can be housed in a relatively small space.
However, because the flat cable used as a lead wire of the cable reel has a high bending rigidity and a larger width dimension, as compared with the wire harness, when the foregoing storage device is applied to the cable reel, a problem occurs in that a space for housing the leading section of the flat cable becomes excessively large. There is also a problem in that the reliability of the connection of the flat cable is lowered, because of an excessive twisting force acting on the flat cable.